1. Field of the Invention
The present invention relates to a friction regenerative pump for use as an electrically-driven fuel pump and more particularly to a friction regenerative pump having a structure intended to improve pump efficiency by reducing leakage of high-pressure fluid from a high pressure outlet to a low pressure intake.
2. Description of the Prior Art
FIG. 5 shows a lateral sectional view of major portions of a conventional side-channel type friction regenerative pump (so-called Wesco pump) and FIG. 6 shows a longitudinal sectional view of the same friction regenerative pump.
In the friction regenerative pump, an impeller (rotor) is rotated within a casing filled with fluid so as to provide the fluid with pressure energy. An outer peripheral end 21 of the impeller 2 is so constructed not to make a contact with an inner face 11 of the casing 1. In FIGS. 5, 6, reference numeral 3 denotes a low-pressure intake, reference numeral 4 denotes a high-pressure outlet, reference numeral 5 denotes a flow path formed in the casing 1, reference numeral 22 denotes a blade groove formed in the impeller 2 and reference numeral 23 denotes a vertical through hole.
However, because as described above, the outer peripheral end 21 of the impeller and the inner face 11 of the casing 1 are constructed not so as to contact each other, a gap 9 is formed between the outer peripheral end 21 of the impeller 2 and the inner face 11 of the casing 1 even in a partition portion (dead point) 6 formed in a section from the high-pressure outlet 4 to the low-pressure intake 3 along an impeller rotation direction a. Thus, high-pressure fluid existing on the side of the high-pressure outlet 4 leaks to the side of the low-pressure intake 3 through the gap 9, so that the leakage reduces its pump efficiency.